1. Field of the Invention
The invention relates to a method and an apparatus for extracting saturated steam formed by the heat of combusting chlorine and hydrogen to produce hydrogen chloride gas in an elongated synthesis oven, the oven including a plurality of segments, and the steam being formed therein by heat exchange between the product of combustion and a heat transfer medium.
2. Description of the Related Art
For the synthesis of gaseous hydrogen chloride from the elements chlorine and hydrogen or from chlorinated hydrocarbons mixed with chlorine, the reaction mixtures are combusted in a substantially hollow, cylindrical oven, in the course of which considerable quantities of heat are produced (approximately 92 kJ/mol of HCl).
The hydrogen chloride gas produced is cooled and generally absorbed by water in an absorber that follows. The oven used for performing the synthesis is made substantially of graphite. Several methods are known for recovering and utilizing the heat liberated in the hydrogen chloride combustion synthesis, for example the indirect cooling of the hydrogen chloride gas in heat exchange with a water circulation loop (German Patent No. DE-PS 857 343). The limited temperature increase to approximately 55.degree. C. substantially restricts the utility of the heat. In another method, it is known to cool hydrogen chloride gas in a first heat exchange to approximately 200.degree. C. with water carried in a circulation loop, to extract some of the absorption heat in a second heat exchange, and to effect flash evaporation of at least some of the heated water in heat exchange with the first loop (German Patent No. DE-PS 33 13 761). In this process, steam is produced at a temperature of approximately 134.degree. C. and a vapor pressure of approximately 3.5 bar which can be used industrially, for instance as process steam.
However, the apparatus required for performing this method, and particularly the adaptation of the quantities of heat extracted at two locations make adaptation to changing operating conditions and changes in the heat requirement difficult.